Corona wire apparatus

ABSTRACT

In electrophotographic apparatus wherein electrostatic charges are provided by corona wire apparatus, an improved corona wire end support block and terminating method in which a corona wire is secured and high voltage shielded internally in a plastic end block. The corona wire extends through a small internal linear bore through the block under a plastic set screw, and then through the lower end of a cut-off access notch, to outside tensioning means such as adjustable weights. The corona wire end is readily cut-off through the access notch so that both the terminated wire end and the fastening are fully inside the block. Thus, the potential for sparking or corona from exposed wire ends or other conductors is greatly reduced. Neither the securing or cut-off of the wire disturbes the desired tension on the wire. Further insulation may be placed in the notch after wire cutoff.

ite States Patent [191 Gallo, JR-

[451 Feb. 12, 1974 CORONA WIRE APPARATUS [75] Inventor: Charles F. Gallo, Jr., Penfield, N.Y.

[7,3] Assignee: Xerox Corporation, Stamford,

' Conn.

22 Filed: Oct. 5, 1972 21] Appl. No.: 295,414

[52] US. Cl 29/25.15, 29/2519, 250/326 [51] Int. Cl. HOllj 9/18 [58] Field of Search 29/2511, 25.15, 25.16, 25.19, 29/252, 452; 250/324, 325, 326; 317/262 A;

[56] References Cited 7 UNITED STATES PATENTS 2,863,063 12/1958 Schulze 317/262 A X 3,339,069 8/1967 Hayne et al 250/326 Primary Examiner-Roy Lake Assistant Examiner.l. W. Davie Attorney, Agent, of Finn.lames J. Ralabate; Paul F. Morgan; Jefi Rothenberg 57 ABSTRACT static charges are provided by corona wire apparatus, an improved corona wire end support block and terminating method in which a corona wire is secured and high voltage shielded internally in a plastic end block. The corona wire extendsthrough a small internal linear bore through the block under a plastic set screw, and then through the lower end of a cut-off access notch, to outside tensioning means such as adjustable weights. The corona wire end is readily cut-off through the access notch so that both the terminated wire end and the fastening are fully inside the block. Thus, the potential for sparking or corona from exposed wire ends or other conductors is greatly reduced. Neither the securing or cut-off of the wire disturbes the desired tension on the wire. Further insulation may be placed in the notch after wire cut-off.

1 CORONA WIRE APPARATUS The present invention relates to corona wire supports and more particularly to a corona wire end block providing internal insulated securing of the corotron wire, internal cut-off, and internal retention of the cut wire end, all of which may be simply and rapidly accomplished without substantially disturbing a present tension applied to the corona wire. I

In an electrophotographic apparatus containing corona wire apparatus, such as a corotron or scorotron, it is necessary to have a suitable means for terminating and retaining the corona wire under tension at its ends. This is commonly done by clamping the wire under the head of a metallic screw. This is a very simple and inexpensive technique, but it has drawbacks. The exposed screw head is at a high voltage potential, and if it has any burrs on it, as it commonly does, undesirable corona or sparking can occur at the burr. Further, during the screw down (clamping) operation, a change in tension may be imposed on the corona wire due to the wire catching in the threads or under the screw head. Additionally, when the wire end projecting beyond the fastening screw is then simply cut off, a sharp end segment is exposed from which undesirable corona or sparking may occur, particularly if this wire end is not supported and maintained in a direction pointing away from the surface being charged. A previously developed remedy for the above problems has been to cover the entire end block with an insulating shield, e.g., US. Pat. No. 2,965,756 by R. G. Vyverberg issued Dec. 20, 1960.

In contrast, the present invention provides a corona wire end support which overcomes the above problems and yet does not require a shield'or any other addi tional components or a more laborous or expensive process of securing the corona wire. In fact, a simplier process is provided which requires less manufacturing skill and is less subject to error and defects. Yet it does not result in any undesirable exposed corona sources, either from the fastening means or the end of the corona wire. This is important from a manufacturing standpoint because modern xerographic machines, for example, contain up to six or more corona wires for the various functions requiring an electrostatic charge.

The exemplary embodiment described hereinbelow discloses the incorporation of the process of the invention in an otherwise conventional exemplary xerographic process and apparatus. This application is.

merely exemplary. The present invention may be utilized in any type of corona wire application or arrangement; shielded, screened or otherwise. Accordingly, said processes and apparatus need not be described in detail herein, since various printed publications and patents and publicly used machines are available which teach details of various suitable exemplary electrophotographic structures, materials and functions to those skilled in the art. Some examples are disclosed in the books Electrophotography by R. M. Schaffert, and Xerography and Related Processes by John H. Dessauer and Harold E. Clark, both first published in 1965 by Focal Press Ltd., London, England, and the numerous patents and other references cited in these books. All of these references are hereby incorporated by reference.

Certain of the individual features disclosed in the present apparatus are, of course, known in other electrical arts. However, they do not teach the present combination or provide the same function or result. Examples are provided in US. Pat. Nos. 3,339,069, 2,879,361, 2,264,075, 1,333,897, and 1,378,952.

Further objects, features and advantages of the present invention pertain to the particular apparatus, steps and details whereby the above-mentioned aspects of the invention are attained. Accordingly, the invention will be better understood by reference to the following description and to the drawings forming a part thereof, which are substantially to scale, wherein:

FIG. 1 is an exemplary corona wire support apparatus and process step in accordance with the present invention; I I

FIG. 2 is a cross-sectional view of the apparatus of FIG. 1 taken along the line 22 of FIG. 1, illustrating another step of the disclosed process; and

FIG. 3 is an additional crosssectional view along the same line 2-2 of FIG. 1 illustrating the apparatus of the invention after the completion of the final steps of the process disclosed hereinbelow.

Referring now to the drawings, FIGS. 1-3, there is illustrated therein a corona wire retaining arrangement 10 in accordance with the present invention. The exemplary apparatus 10 is supporting an exemplary corona wire 12 over an exemplary chargeable surface 13, e.g., a xerographic photoreceptor drum. The apparatus 10 here comprises a first end block 14 supporting and insulating the first end of the corona wire 12, and second end block 16 supporting and insulating the second or terminating end of the corona wire 12.

The first end block 14 is here further adapted to provide the connection to the corona high voltage power supply 18. This is accomplished in a shielded manner internally of the first end block 14 by a female connector 20 extending internally into the first end block 14 under a first set screw 22. The female connector 20 is conventionally connected to the high voltage power supply 18. The first set screw 22 is preferably entirely formed from a plastic or other suitable high voltage insulating material, as are both of the end blocks. The first set screw 22 internally holds and abuts the first end of the corona wire 12 against the connector 20. The corona wire 12 extends thereto through an internal passageway in the first end block 14 extending up to the set screw 22.

Considereing now in greater detail the second end block 16, which is illustrated in enlarged cross-section in FIGS. 2 and 3, it may be seen that it is preferably a unitary, homogeneous block of simple construction and configuration formed in a conventional manner from any suitable plastic or other material having appropriate high voltage insulating properties. The only additional component of the end block is a second set screw 24 therein which provides the fastening means for the corona wire. The second set screw 24 may be of the same or other suitable insulating material. It may be seen that the set screw 24 is tightly threadably fitted in a corresponding cylindrical threaded hole 26 extending from the exterior surface of the block 116 down into the interior thereof at right angles to the corona wire 12. The screw 24 is adapted to both secure grip the co- I rona wire 12 as well as to fill and thereby electrically insulate the threaded hole 26. It may be seen that the set screw 24 provides securing of the corona wire 12 internally of the block 16 by means which are operable externally thereof. No conductive elements are exposed by this fastening arrangement, nor is the corona wire 12 itself.

It may be seen that the corona wire 12 is continuously closely laterally confined and insulated within the interior of the block 16 by a surrounding cylindrical bore 28 extending linearly through the center of the block and having a diameter only slightly larger than the corona wire 12. The bore 28 provides a sufficiently loose fit to allow the corona wire 12 to be slidably inserted completely therethrough. It may be seen that the bore 28 opens at both ends of the block 16. As is shown in FIGS. 1 and 2, for the process discussed below a free end 36 of the wire 12 is initially extended beyond the outlet of the bore 28 for a distance beyond the block sufficient to allow a suitable tensioning grip to be made on the wire.

Spaced internally from the ends of the block 16, and also spaced from the set screw 24, is a knife slit 30 extending from the surface of the block into its interior extending through and slightly beyond the bore 28. The slit 30 is adapted to provide an access aperture for the severing of the corona wire 12 internally of the block 16. For this function the knife slit 30 perpendicularly intersects and communicates with the bore 28 only within the central interior of the block. Preferably, as shown, the slit 30 is smoothly inwardly tapered as it extends into the block so as to provide a guide for severing means such as a knife blade 32 shown in FIG. 2. Thus, it guides the knife 32 down into severing contact with the corona wire 12 in the bore 28, for severing it flush with a wall of slit 30. The opening or exposure of the bore 28 in the bottom of the slit 30 is very short, so that the potential movement of the exposed wire is restrained by the bore 28. Thus, clean shearing off of the end of the wire 12 at a precise, consistent location is readily accomplished to provide a cut end 34 as shown in FIG. 3. It may be seen that the cut end 34 is retained within the bore 28 deep in the interior of the block 16. The cut end 34 is thus aligned with the corona wire 12 and spaced from the outlet opening of the bore 28 and from the free end 36 of the wire 12.

Corona wire securing and terminating in the apparatus described herein is very simple and rapid, and is illustrated consecutively in FIGS. l-3. The end of the corona wire 12 is first simply threaded through the bore 28. A desired tension is then applied to the extending free end 36 through tension means 38, which may comprise an adjustable weight 40 removably clamped to the free end as in FIG. 1, or springs or other suitable tensioning means 38. Since the corona wire 12 is freely slidable through the bore 28, a uniform tension is applied by the tensioning means 38 along the entire corona wire 12. The central, corona generating section of the corona wire 12 (between the two end blocks) is then clamped to retain this pre-set tension thereon simply by threading down the recessed set screw 24 onto the wire 12.

The tension on the wire 12 is not significantly altered by the twisting action of the screw 24 because the wire 12 is prevented from twisting during the tightening operation by the fact that the bore 28 restrains all lateral movement of the wire directly up to each side of the base of the screw 24. Also, tension cannot be imparted on the wire 12 by overtightening of the set screw 24 because the threaded hole 26 preferably extends down into communication with, but not substantially beyond, the bore 28. Thus, the screw 24 base cannot be screwed downwardly past the line of the corona wire 12.

A spacer or washer can be placed underneath the set screw 24, between the screw base and the wire 12. This even further prevents any possibility of twisting, denting or scratching the wire.

Then, as illustrated in FIG. 2, a knife 32 or other suitable severing means can be uncritically inserted into the wide surface opening of the slit 30 and slid down into the narrowing tapered opening to sever the wire 12 therein. This cannot afiect the tension on the central portion of the wire 12, since the wire is already secured by the set screw 24. The severing is accomplished outside of the central portion of the corona wire, between the set screw 24 and the tension means 38.

Preferably during the severing operation the tension continues to be applied. This assists in the severing operation and also automatically provides for a further step of removing the severed end of the wire from the interior of the block 16. When the wire is severed the tension means 38 automatically pulls away the free end 36 of the corona wire. This then pulls out of the block 16 the portion of the corona wire 12 within the interior of the block which has been cut off at the slit 30. As may be seen in FIG. 3 this leaves a long empty segment of the bore 28 between the cut wire end 34 and the outlet of the bore 28. This in itself provides, without more, good electrical isolation of the cut end 34 since it may be seen that the only exposed electrical air path from the cut end 34 to the exterior of the block 16 is either through this long empty section of the bore 28 or through the substantially equally elongated passageway up through the knife slit 30 to the exterior of the block.

Even the above two restricted electrical paths to the cut end 34 may be readily sealed, as illustrated in FIG. 3, by applying a single sealant member 42 in the form of a blob of conventional suitable electrical sealant or a solid plastic wedge insert. Any suitable hardenable liquid plastic or rubber sealant may be used, for example. The configuration of the knife slit 30 provides for retension of the sealant 42 and also for guiding it downwardly into overlying relationship with both the cut end 34 of the wire 12 and also into the segment of the bore 28 with which it communicates. Thus, a single application of sealant 42 envelops, fills and seals both the cut end 34, the bore 28, and the knife slit 30 simultaneously. Since no other portion of the corona wire 12 is exposed at any point within the block 16, complete sealing of the entire segment of the corona wire within the block is thereby provided. However, as indicated above, the sealant 42 is not needed in many applications due to the high degree of isolation provided by the structure of the end block 16 itself when the wire is severed in accordance with the above teachings.

While the above step is preferably accomplished with the block 16 in the orientation shown, it will be appreciated that in the installation of the apparatus 10 in a xerographic machine that the slit 30 may be faced downward so as to discourage toner accumulation therein.

In conclusion, it may be seen that there has been dis closed herein a novel and improved apparatus and method for supporting and terminating corona wires in electrophotographic apparatus, having numerous advantages in simplicity, economy, wire tension control and high voltage insulation. The exemplary embodiments described herein are presently considered to be preferred; however, it is contemplated that numerous further variations in modifications within the purview of those skilled in the art can be made herein. The following claims are intended to cover all such variations and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In electrophotographic apparatus wherein electrostatic charges are provided by corona wire apparatus, the improvement in the corona wire apparatus comprising;

an insulative corona wire end support block,

said end block having a corona wire confining bore extending internally therethrough with inlet and outlet openings from said block;

insulative fastening means for securing said corona wire within said bore under tension,

said fastening means extending from the exterior of said block into communication with said bore internally within said block;

and a corona wire severing access aperture extending from the exterior of said block into communication with said bore internally within said block providing access to said bore for severing a corona wire therein,

said severing access aperture being substantially spaced from said inlet and outlet openings of said bore so that the end of a corona wire severed in said aperture is internal said block.

2. The apparatus of claim 1 wherein said bore extends substantially linearly through said block.

3. The apparatus of claim 1 wherein said corona wire severing access aperture comprises a smooth walled slit extending inwardly into said block substantially perpendicular said bore, extending slightly beyond said bore, adapted to guide severing means into severing contact with a corona wire in said bore.

4. The apparatus of claim 1 wherein said corona wire severing aperture is the only exposed opening in said bore other than said inlet and outlet openings.

5. The apparatus of claim 4 wherein said corona wire access opening is adapted to retain insulative sealing means therein in sealing communication with said bore.

6. The apparatus of claim 3 wherein said corona wire severing aperture is the only exposed opening in said bore other than said inlet and outlet openings and is generally wedge shaped, tapering together inwardly from a wide opening at the exterior of said block to an apex intersecting said bore.

7. The apparatus of claim 5 wherein said corona wire access aperture contains insulative sealing means commonly sealing said bore and said access aperture.

8. The apparatus of claim 2 wherein said bore is only slightly larger than said corona wire so as to confine lateral movement of said corona wire.

9. The apparatus of claim 3 wherein said fastening means comprises a cylindrical screw-threaded aperture in said block extending through, but not substantially beyond, said bore, perpendicular to said bore, and a screw of insulative material threadable into said aperture into intersection with said bore.

110. The apparatus of claim 1 wherein said bore is substantially linear and contains a corona wire extending slidably therethrough, said corona wire having a free end extending from said outlet opening, and wherein tension means connect with said free end for placing said corona wire under tension.

11. The apparatus of claim 1 including a further end block for retaining an opposite end of said corona wire internally therein and containing internal high voltage connecting means for connecting with said corona wire internally of said further end block.

12. A method of tensioning and severing a corona wire and providing electrical insulation for the severed end of the corona wire, comprising the steps of;

threading a segment of said wire internally through a surrounding insulative block until a free end of said wire extends beyond said block;

placing said wire under tension by applying tension to said free end of said wire;

clamping said wire at an intermediate point internally of said block; then severing said wire internally within said block between said intermediate point and said free end of said wire at a severing point thereon internal said block through an access aperture in said block;

then removing said free end of said wire, and the connecting severed portion of said wire up to said severing point, by said tension on said free end of said wire.

13. The method of claim 12 further including the step of sealing said wire internally within said block at said severing point to fully insulate said wire internally within said block. 

1. In electrophotographic apparatus wherein electrostatic charges are provided by corona wire apparatus, the improvement in the corona wire apparatus comprising; an insulative corona wire end support block, said eNd block having a corona wire confining bore extending internally therethrough with inlet and outlet openings from said block; insulative fastening means for securing said corona wire within said bore under tension, said fastening means extending from the exterior of said block into communication with said bore internally within said block; and a corona wire severing access aperture extending from the exterior of said block into communication with said bore internally within said block providing access to said bore for severing a corona wire therein, said severing access aperture being substantially spaced from said inlet and outlet openings of said bore so that the end of a corona wire severed in said aperture is internal said block.
 2. The apparatus of claim 1 wherein said bore extends substantially linearly through said block.
 3. The apparatus of claim 1 wherein said corona wire severing access aperture comprises a smooth walled slit extending inwardly into said block substantially perpendicular said bore, extending slightly beyond said bore, adapted to guide severing means into severing contact with a corona wire in said bore.
 4. The apparatus of claim 1 wherein said corona wire severing aperture is the only exposed opening in said bore other than said inlet and outlet openings.
 5. The apparatus of claim 4 wherein said corona wire access opening is adapted to retain insulative sealing means therein in sealing communication with said bore.
 6. The apparatus of claim 3 wherein said corona wire severing aperture is the only exposed opening in said bore other than said inlet and outlet openings and is generally wedge shaped, tapering together inwardly from a wide opening at the exterior of said block to an apex intersecting said bore.
 7. The apparatus of claim 5 wherein said corona wire access aperture contains insulative sealing means commonly sealing said bore and said access aperture.
 8. The apparatus of claim 2 wherein said bore is only slightly larger than said corona wire so as to confine lateral movement of said corona wire.
 9. The apparatus of claim 8 wherein said fastening means comprises a cylindrical screw-threaded aperture in said block extending through, but not substantially beyond, said bore, perpendicular to said bore, and a screw of insulative material threadable into said aperture into intersection with said bore.
 10. The apparatus of claim 1 wherein said bore is substantially linear and contains a corona wire extending slidably therethrough, said corona wire having a free end extending from said outlet opening, and wherein tension means connect with said free end for placing said corona wire under tension.
 11. The apparatus of claim 1 including a further end block for retaining an opposite end of said corona wire internally therein and containing internal high voltage connecting means for connecting with said corona wire internally of said further end block.
 12. A method of tensioning and severing a corona wire and providing electrical insulation for the severed end of the corona wire, comprising the steps of; threading a segment of said wire internally through a surrounding insulative block until a free end of said wire extends beyond said block; placing said wire under tension by applying tension to said free end of said wire; clamping said wire at an intermediate point internally of said block; then severing said wire internally within said block between said intermediate point and said free end of said wire at a severing point thereon internal said block through an access aperture in said block; then removing said free end of said wire, and the connecting severed portion of said wire up to said severing point, by said tension on said free end of said wire.
 13. The method of claim 12 further including the step of sealing said wire internally within said block at said severing point to fully insulate said wire internally within said block. 